For example, a saw blade such as a band saw blade, a circular saw blade and the like, as shown in FIGS. 12(A) and 12(B), is conventionally known. Tn this saw blade, a straight tooth 101S, a left-hand set tooth 103L and a right-hand set tooth 103R are set to one group. In another conventional example of the saw blade, as shown in FIGS. 13(A) and 13(B), a straight tooth 105S, a left-hand set tooth 107L, a right-hand set tooth 107R, a left-hand set tooth 109L and a right-hand set tooth 109R are set to one group.
The left-hand set teeth 103L, 107L, 109L and the right-hand set teeth 103R, 107R, 109R in the respective saw blades are independently bent. As shown in FIG. 14, when a material W is cut by each of the saw blades, the left-hand set teeth 103L, 107L, 109L and the right-hand set teeth 103R, 107R, 109R prevent an interference of the material W with a body portion 111 in each of the saw blades.
However, since the left-hand set teeth 103L, 107L, 109L and the right-hand set teeth 103R, 107R, 109R in the respective saw blades are independently formed, the material W is cut by each of the saw blades vibrating leftward and rightward when each of the left-band set teeth 103L, 107L, 109L and the right-hand set teeth 103R, 107R, 109R cuts the material W. As shown in FIGS. 15A, 15B and 15C, a so-called ghost pattern 113 appears in a cutting plane of the material W cut by the cutting operation.
This phenomenon of vibration of each of the saw blades leftward and rightward particularly causes a problem in performing a heavy cutting operation. When a feed speed exceeds a certain limit, a wavy pattern 115 having an amount of waviness "a" occurs in the material W as shown in FIGS. 16A, 16B and 16C and may lead to a cutting deviation.
The left-hand and right-hand set teeth in each of the saw blades shown in FIGS. 12A, 12B and FIGS. 13A, 13B3 are shifted forward and backward in an advancing direction of each of the saw blades. Accordingly, the left-hand and right-hand set teeth are vibrated leftward and rightward with respect to this advancing direction so that the ghost pattern 113 occurs. Further, the wavy pattern 115 occurs in cutting operation for increasing a cutting amount. Accordingly, as a countermeasure for preventing each of the saw blades from being vibrated leftward and rightward, it is necessary to arrange such that that the left-hand and right-hand set teeth simultaneously cut the material while opposing to each other in the leftward and rightward direction.
A saw blade as shown in FIG. 17 is known as a dovetail type saw blade for simultaneously cutting the material leftward and rightward in this same tooth. Namely, in FIG. 17, the saw blade is constructed by a preceding tooth 117 and a succeeding tooth 119 having a dovetail shape. The preceding tooth 117 is set to a high tooth and the succeeding tooth 119 is set to a low tooth.
However, as shown in FIG. 17, a face d must be finished by polishing work to obtain a side face relief angle .alpha.' so that it takes much time to perform the polishing work. As shown in U.S. Pat. No. 3,576,061, a similar problem is also caused when an angle of inclination of a rake face is formed.
Further, a chain saw as shown in U.S. Pat. No. 3,367,216 is used to process wood, and a tooth edge of the chain saw is insufficient in strength to cut a metal. A saw blade as shown in U.S. Pat. No. 3,651,841 is also used for a wood material and an organic material (cork, rubber, bone and the like.). There is also a case in which this saw blade is used to cut a material. However, in this case, the strength of a tooth edge of the saw blade is also insufficient. In particular, this saw blade is not suitable for heavy cutting.
In a circular saw shown in each of Japanese published Utility Model (KOKOKU) No. 62-28336 and Japanese published Patent (KOKOKU) No. 62-5730, a tooth line is divided at the tooth line center of a tooth edge in its thickness direction and is perpendicular to a side face of a body portion. Chips produced during cutting is stored into gullets. When the chips are melted and attached to the saw, no chip is sufficiently removed from the saw by a chip removing apparatus (such as a wire brush, etc.) so that tooth edge chipping is caused by the melting attachment of the chips. Further, when a tooth edge of a preceding tooth is chipped, and wearing of a succeeding tooth having a groove in a tooth edge center portion progresses so that a cutting amount becomes greater than a depth of the tooth edge center groove of the succeeding tooth, no chip is divided and cutting resistance is increased and a melting attachment strength is also increased so that tooth edges are often chipped.
Further, in Japanese laid-open patent (KOKAI) No. 54-45895 as a prior example, a V-shaped groove is formed in a central portion of a tooth edge in a saw blade so that the tooth edge is divided into left-hand and right-hand portions and their end tip portions are projected from a body portion side face of the saw blade.
In this construction, the divided left-hand and right-hand tooth edge portions are sharpened so that a tooth edge strength is small and no material can be cut at all when the material is a metal.
An object of this invention is to provide a saw blade in which left-hand and right-hand set teeth in a succeeding tooth with respect to a preceding tooth can be bend quickly simultaneously in left-hand and right-hand directions and almost no ghost pattern is caused and no wavy pattern is caused during cutting operation, and a cutting deviation amount during cutting operation is small so that a stabler cutting operation can be performed.